Gastropoda

Class Gastropoda (Snails)
Courtesy of the Cacapon InstituteOperculate snails: Flat lid-like structure called an operculum that can seal the body of the snail inside the shell; the whorls of the shell bulge out distinctively to the sides (inflated); most have their opening on the right when the narrow end is held up; shells often extended into a spiral shape.  Non-operculate snails: No operculum; the whorls of the shell do not distinctly bulge out to the sides; often the shells of most kinds are shaped like a low flat cone or coiled flat instead of being extended in a spiral shape.  Typical size range for most snails is VS-L, which includes the shell.  For more information visit Marshall University’s Aquatic Snails of West Virginia. 

Operculate snails (Sub-class Prosobranchia)

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Hydrobiidae (Pebble snail): Shell is whorled and bulges out to the side (inflated); opens to the right when the narrow end is held up.  The family is very diverse in shell size and shape; shell shape can range from conical (cone-like) to spherical (rounded). Clinger/crawler; Scraper; (L)(F)
Pleuroceridae (Rock snail): Shell is spiraled and whorled but does not budge out to the side (flattened); opens to the right when the narrow end is held up; operculum is small and can be pulled into the shell. Clinger/crawler; Scraper; (L)(F)
Valvatidae (Valve snail): Shell is small, flattened and conical shaped: operculum is multi-spiraled. Clinger/crawler; Scraper (L)(S)
Viviparidae (River snail): Shell is whorled and bulges out to the side (inflated); opens to the right when the narrow end is held up; operculum has concentric lines, which are slightly off-center. Clinger/crawler; Scraper; (M)(S)

Non-operculate snails (Sub-class Pulmonata)

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Ancylidae (Limpet): Shell shaped like a low flat cone. Clinger/burrower; Scraper; (H)(F)
Lymnaeidae (Pond snail): Shell vaiable from long needle-like spirals to flat cones. Most often found in waters with high mineral content. Clinger/crawler; Scraper; (H)(S/F)

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Planorbidae (Orb snail): Shell is coiled flat instead of extended in a spiral.  Clinger/burrower; Scraper; (M)(S/F)

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Physidae (Pouch snail): Shell is high, spiraled, with a slight bulge; opens to the left when the narrow end is held up.  Clinger/crawler; Scraper; (H)(S/F)

 
Note: North American streams, rivers, and lakes support the richest diversity of freshwater mollusks on the planet. Over 650 species of snails and 300 species of freshwater mussels have been described so far. Click-Here to learn more.  

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